Quantity of 1.5g brass containing Cu,Zn reacts with `3M,HNO_(3)` solution, the following reactions takes place
`Cu +HNO_(3) rarr Cu^(2+) +NO_(2) +H_(2)O`
`Zn +H^(+) +NO_(3)^(-) rarr NH_(4)^(+) +ZN^(2+) +H_(2)O` (un balanced)
The liberated `NO_(2)(g)` is found to occupy 1.04 litre at `25^(@)C` and 1 atm pressure. Now answer the following question
% of copper in the alloy is

Options

A. 80
B. 90
C. 85
D. 10

Answer

B

Explanation

`Cu +4HNO_(3) rarr Cu(NO_(3))_(2) +2NO_(2)+2H_(2)O`
no of mol of copper `=(1)/(2)`no of mol of
`NO_(2) = (PV)/(RT) = (1 xx 1.04)/(0.0821 xx 298)`
`:.` no of mol of copper `= 0.021`
weight of copper `=0.021 xx 63.5 = 1.35g`
% copper `=(1.35)/(1.5) xx 100 = 90`